Cells coordinate the regulation of metabolism, growth and the cell division cycle in response to the environment. For example, in response to unfavorable environmental conditions, yeast and other organisms slow down growth and regulate their metabolism to store carbohydrates, which are crucially important for stress resistance and long-term survival. Yeast cells periodically utilize and rebuild these carbohydrate reserves, which is a key element of the phenomenon known as metabolic cycling. Based on the observation that cell division is correlated with specific phases of the metabolic cycle, it ha been proposed that the cell cycle is gated by the metabolic cycle. However, the hierarchy of regulation and the contribution of carbohydrate storage metabolism to cell cycle control remain unclear and heavily debated. Successful completion of our aims will result in resolving how the metabolic and the cell division cycle are mechanistically linked and whether their regulation is hierarchical or interdependent. To achieve our aims, we will employ microfluidics and modern imaging and signal processing methods to develop a novel experimental platform for examining metabolic cycling in individual yeast cells. The application of microfluidic cultivation offers a unique advantage for studying metabolism. In contrast to existing methods, rapid and constant flow during microfluidic cultivation allows direct specification of extracellular nutrient concentrations independent of cell density. Thus, we expect our innovative low-cost platform to be widely adopted by the community of researchers working on metabolic regulation. Our specific aims include: (Aim1) Visualize the metabolic and the cell division cycle in single cells b developing fluorescent reporters for metabolic regulation to be used together with existing reporters for the cell cycle; (Aim2) Use this set of reporters in conjunction with genetic and chemical manipulations of signaling pathways to determine the molecular mechanism(s) linking metabolic and cell cycle regulation. Relevance to public health: In humans, despite the fact that the Warburg Effect -the upregulation of aerobic glycolysis- and other metabolic malfunctions in cancer were described decades ago, the underlying molecular mechanisms are only gradually being uncovered. Specifically, it remains unclear whether metabolic alterations are the cause or an effect of oncogenesis. Unraveling metabolic processes in more tractable organisms, such as yeast, can greatly facilitate their understanding in complex human systems and thereby contribute to identifying novel drug targets affecting metabolism. PUBLIC HEALTH RELEVANCE: Cells coordinate the regulation of metabolism, growth and the cell division cycle in response to the environment. We aim to determine how the metabolic and the cell division cycle are mechanistically linked and whether their regulation is hierarchical or interdependent.